Given that colorectal cancer remains a leading cause of death from cancer in the United States, there is an unmet need to develop safer and more efficacious agents for treatment and prevention of colorectal cancer. Numerous studies report that the nonsteroidal anti-inflammatory drug (NSAID), sulindac is highly effective for the treatment of precancerous adenomas in individuals with familial adenomatous polyposis and shows promising anticancer activity in preclinical animal models; however, the adverse side effects resulting from cyclooxygenase (COX) inhibition limit the long-term use of sulindac for chemoprevention. Our previous study reported that two new non-COX inhibitory derivatives, sulindac sulfide amide (SSA) and sulindac benzylamine (SBA), can inhibit colorectal tumor cell growth with better potency and improved efficacy when compared to sulindac sulfide (SS). These results imply that anticancer activity of sulindac might attribute to other underlying mechanisms distinct from COX inhibition. In this application, we aim to study the new molecular mechanisms responsible for anticancer activity of sulindac and non-COX inhibitory derivatives in prevention of colorectal tumor progression and metastasis. Our recent results show that SS at sub-cytotoxic concentrations can efficiently inhibit the invasion of human colon tumor cells, and this action is demonstrated to involve microRNAs (miRNAs), which are a set of small non-coding RNA molecules acting as the master regulators in control of human gene expression. A tumor suppressor miRNA, miR-200, is found to be up-regulated by SS and its non-COX inhibitory derivatives through the signaling pathway mediated by the transcriptional repressor snail. Given the documented tumor suppressive roles in promotion of apoptosis and inhibition of metastasis, we hypothesize that miR-200 is a key factor to mediate the anticancer activity of SSA and SBA in colorectal cancer. Three specific aims are proposed to address this hypothesis: (1) to study the mechanistic basis of miR- 200 in mediation of anticancer activities of SSA and SBA in vitro; (2) to study the role of miR-200 in mediating anticancer activities of sulindac in vivo; (3) to assess the clinical relevance of snail/miR-200/E-cadherin to human colorectal cancer progression. This application is being submitted in response to PA-12-213 and will address two research objectives: determine the molecular pathways targeted by non-coding RNAs (ncRNAs) that predispose to cancer initiation or progression and determine whether interfering with oncogenic ncRNAs processing, target selection, or associated pathways prevent cancer progression. The proposed studies have a potential to impact human health by: 1) providing a mechanistic rationale in support of an ongoing national clinical trial studying a new indication of sulindac in prevention of colorectal cancer progression; 2) evaluating the novel non-COX inhibitory directives of sulindac to accelerate their preclinical development; and 3) identifying new therapeutic targets and/or biomarkers for clinical trials.